1. Field of the Invention
The invention relates to a display apparatus and an optical system, and more particularly, to a projection apparatus and an illumination system.
2. Description of Related Art
Recently, projection apparatuses using solid state light sources such as, light emitting diodes (LEDs) and laser diodes, have gradually held considerable market share. The luminescence efficiency of the LEDs is about 5% to 8%, and the LEDs have different luminescence spectrums available for selection, including red, green and blue spectrums. The LEDs have excellent luminescence spectrums, i.e. having a high spectrum peak value and a narrow spectrum width, and, therefore, can be used as pure color light sources for projectors.
On the other hand, the laser diodes have luminescence efficiency greater than 20%. In order to break through the limit of the LEDs as light sources, using a laser source to excite a phosphor powder to produce the pure color light source for projectors has been gradually developed. The two types of light sources are the main stream of the solid state light sources for current projectors.
In order to achieve a sufficient output luminance, a laser projection apparatus can use an array of multiple laser diodes, and laser beams emitted by the laser diodes are focused onto the phosphor layer to produce a fluorescence having a sufficient intensity. The array of laser diodes can produce a rather high light output power to excite the phosphor and the number of the light sources can be flexibly adjusted to achieve different levels of luminance for projectors. Therefore, projection apparatus using this type of light sources have huge potential to replace the projection apparatus using the conventional ultra high pressure lamp (UHP lamp) as a light source and become the main stream of next generation projection apparatus.
US Patent Publication No. 20100328632 disclosed a light source device including a light source, a dichroic mirror, three reflecting mirrors, a color wheel, and a light integration rod. US Patent Publication No. 20110205502 disclosed a projection apparatus including a blue light source, a red light source, a light volume controller, an integrator, a color wheel, a dichroic mirror, reflecting mirrors, a light valve, a light sensor, a light volume regulator and a projection lens. U.S. Pat. No. 7,461,950 disclosed a light source device including a light source, a light converting section, a color wheel, a UV-IR cutting filter, a light-polarization converting element, an integrator, an illumination optical system, a light modulating device, and a projection apparatus. The color wheel is operable synchronously with the light converting section to generate a light having sufficient brightness and purified color.